Administration: Sync admin-ui Page header accessibility backport from Gutenberg

[itzmekhokan]

Mirror the changes from Gutenberg PR WordPress/gutenberg#78002 (which backports WordPress/gutenberg#77617 and WordPress/gutenberg#78001 to the wp/7.0 branch) into the auto-generated wordpress-develop bundles for the Connectors and Font Library admin screens.

Two of the three accessibility issues raised in the ticket are addressed by this sync:

• Page heading is now an h1 instead of an h2. The bundled Header component's default headingLevel is bumped from 2 to 1, and the now-redundant explicit headingLevel: 1 overrides at the Connectors and Font Library route stages are dropped.
• The inappropriate <header> landmark inside the page's region landmark is removed by dropping the render: <header /> prop on the Stack wrapping the page header, eliminating the nested banner landmark.

The third issue (full-white body background) still needs to land upstream in Gutenberg per the latest comment on the ticket.

Bundles updated for both the readable and minified outputs of:

• src/wp-includes/build/routes/connectors-home/content.js
• src/wp-includes/build/routes/connectors-home/content.min.js
• src/wp-includes/build/routes/font-list/content.js
• src/wp-includes/build/routes/font-list/content.min.js

The version hash in each content.min.asset.php is bumped to the md5 of the new minified bundle so cached browser copies are invalidated; the next official Gutenberg sync will overwrite these with the build pipeline's canonical hashes.

Props joedolson, afercia, hbhalodia, wildworks.
See #65100.

Trac ticket: https://core.trac.wordpress.org/ticket/65100

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